taro-ui 3.0 designWidth 配置为 375 放大问题

参考issues: https://github.com/NervJS/taro-ui/issues/1069#issuecomment-661600488

详细解决方案:
① 安装 "postcss-px-scale"

npm i postcss-px-scale --save-dev

② config/index.js中设置designWidth，deviceRatio

designWidth: 375,
deviceRatio: {
    640: 2.34 / 2,
    750: 1,
    375: 1 / 2,
    828: 1.81 / 2,
}

③ config/index.js 中添加 postcss-px-scale 配置
mini postcss 部分添加

"postcss-px-scale": {
    "enable": true,
     "config": {
        "scale": 0.5, // 缩放为 1/2
        "units": "rpx",
        "includes": ["taro-ui"]
    }
}

h5 postcss部分添加

"postcss-px-scale": {
    "enable": true,
    "config": {
        "scale": 0.5, // 缩放为 1/2
        "units": "rem",
        "includes": ["taro-ui"]
    }
}